When Kevin married Abi, Debbie did mention it was his fourth marriage (including two to Sally). I think the writing team must all watch the classic episodes - we’re seeing a lot more references to past characters and situations these days.
I remember when it came out that Jenny’s son had died, Kevin said ‘I don’t know what it’s like to lose a child’ - and a large number of viewers said ‘Er, yes he does!’ I later read that Michael Le Vell had actually pointed this out to the producers, but they’d run with the script anyway. I’d like to think that wouldn’t happen now.